1. Field of the Invention
The present invention relates to a capacitor module for use in an inverter device, an inverter, and a capacitor module, and more particularly to a capacitor module for use in an inverter, an inverter, and a capacitor module that are suitably used for a power module and the like.
2. Description of the Related Art
An inverter comprises a switching element and a capacitor. As shown in FIG. 10, the terminal 52 of a capacitor 51 is electrically connected to a switching element 53. Although only a single terminal 52 is shown in FIG. 10, a pair of terminals having polarities different from each other are each connected to the switching element 53. In a real inverter, the capacitor 51 and the switching element 53 are installed in an insulative housing (not shown).
As in the case of other electronic equipment or electronic components, inverters are also required to be reduced in size. Japanese Unexamined Patent Publication No. 9-308265 discloses an inverter device for use in an electric car that is of a structure having a small footprint so as to permit an effective use of the space for installation.
In the above-mentioned prior art inverter, a smoothing capacitor is disposed above a switching module by bending an input conduction plate connected to the input terminal portion of the switching module, and connecting the smoothing capacitor consisting of an electrolytic capacitor to the input conduction plate bent. Herein, since the smoothing capacitor consisting of a relatively large-sized electrolytic capacitor is disposed above the switching module, the reduction in the space for installation has been achieved.
As described above, in a conventional inverter, since an electrolytic capacitor with a large volume has been used, electric connection portion between a capacitor and a switching module, for example, the above-mentioned input conduction plate has a certain length. This electric connection portion has, therefore, inevitably generated an inductance component.
In order to reduce the inductance component, it is preferable to dispose a capacitor in a closer vicinity of the switching module. Accordingly, a capacitor has hitherto been disposed as close as possible to the switching module.
However, since the electrolytic capacitor has a large volume as described above and hence the electric connection portion between the electrolytic capacitor and the switching module has a certain length, there has been a limit to the reduction in inductance component.
Accordingly, it is an object of the present invention to overcome the above-mentioned drawback associated with the prior art, and to provide a capacitor module for use in an inverter, an inverter, and a capacitor module capable of effectively reducing the inductance component generated in the electric connection portion between the capacitor module and the switching module in an inverter.
A first invention of the present application is a capacitor module for use in an inverter, comprising: a plurality of ceramic capacitors having a first terminal and a second terminal; and a substrate which has a first surface and a second surface opposed to each other, and a plurality of via holes extending through from the first surface to the second surface, and on which the plural ceramic capacitors and a switching module are mounted, wherein: a first conductor is formed on the first surface of the substrate, wherein the first terminals of the plural ceramic capacitors are connected to the first conductor; a second conductor is formed on the second surface of the substrate, wherein the second terminals of the plural ceramic capacitors are connected to the second conductor through the via holes; and first and second terminal mounting portions, where the first and second terminals of the switching module are mounted, are formed on the substrate, wherein the first and second terminal mounting portions are electrically connected to the first and second conductors, respectively.
In a specified aspect of the first invention, the first and second conductor are each formed substantially all over the first and second surfaces.
A substrate constituted of synthetic resin or ceramic is suitable for above-mentioned substrate to be used in the first invention. However, the material for a substrate is not particularly limited to synthetic resin or ceramic.
A second invention of the present application is a capacitor module for use in an inverter, comprising: a plurality of ceramic capacitors having a first terminal and a second terminal; and a substrate which has a first surface and a second surface opposed to each other, and a plurality of via holes extending through from the first surface to the second surface, and on which the plural ceramic capacitors and a switching module are mounted, wherein: the substrate has an insulating sheet, and a first and second metallic plates constituting the first and second conductors laminated on both sides of the insulating sheet, wherein the plural ceramic capacitors are mounted on the first conductor, the first terminals of the plurality of ceramic capacitors being connected to the first conductor; the second terminals of the plurality of ceramic capacitors are connected to the second conductor through the via holes; and first and second terminal mounting portions, where the first and second terminals of the switching module are mounted, are formed on the first and second metallic plates.
In the first and second inventions (hereinafter referred to the present invention), it is preferable that a monolithic capacitor is used as above-mentioned ceramic capacitor.
In a specified aspect of the first and second inventions, at least the portions connected to the first and second terminals of the capacitor, and the first and second mounting portions are exposed on the first and second conductors, and an insulating coating is formed over the remaining area.
More preferably, the insulating coating is constituted of a material having a higher thermal conductivity than air.
In another aspect of the present invention, a synthetic resin having a higher thermal conductivity than air is charged between the ceramic capacitor and the substrate.
In a still another aspect of the present invention, an exterior resin layer for covering the whole of the capacitor module is further provided.
The inverter in accordance with the present invention is characterized in that it comprises a capacitor module in accordance with the first and second inventions, and a switching module which is mounted on the first and second terminal mounting portions disposed on the substrate of the capacitor module.
The capacitor module in accordance with the present invention is characterized in that it comprises: a plurality of ceramic capacitors having a first terminal and a second terminal; and a substrate which has a first surface and a second surface opposed to each other, and a plurality of via holes extending through from the first surface to the second surface, and on which the plural ceramic capacitors are mounted, wherein: a plurality of ceramic capacitors are formed on the first surface of the substrate, wherein a first conductor is formed on the first surface, the first terminals of the plural ceramic capacitors being connected to the first conductor; a second conductor is formed on the second surface of the substrate, wherein the second terminals of the plurality of ceramic capacitors are connected to the first conductors through the via holes.
In the capacitor module in accordance with the present invention, it is preferable that a monolithic capacitor is used as the ceramic capacitor.